PCT International Publication No. WO 01/15109 describes a magnetic sensor, in which a generated primary magnetic field is changed by an object and this change is measured. The magnitude of the changes depends on the magnetic properties of the object, that is, whether they are paramagnetic, diamagnetic or ferromagnetic properties. These properties are characterized by magnetic susceptibility and permeability. This is because of the magnetic behavior and the inner structure of the electron shell of the existing atoms and molecules. Thus the subject matter of this application is a measuring device, in which the primary magnetic field is influenced.
The disadvantage of this is that the measurement of the attenuation of the primary variable magnetic field is sensitive to interference effects and that there is no possibility for measuring the distance to the object.